Communications system

ABSTRACT

A method performed by a base station includes generating a request for resource status information, sending the generated request to a neighboring base station, receiving one or more resource status update messages from the neighboring base station in response to the requested resource status information, and performing load balancing operations in dependence upon the received one or more resource status update messages.

The present Application is a Continuation Application of U.S. patentapplication Ser. No. 13/678,875, filed on Nov. 16, 2012, which was aContinuation Application of U.S. patent application Ser. No. 12/735,418,filed on Jul. 14, 2010, now U.S. Pat. No. 8,442,547 B2, which was aNational Stage Application No. PCT/JP2009/052120, filed on Feb. 3, 2009,which was based on the United Kingdom Patent Application No. 0802023.2,filed on Feb. 4, 2008, the entire contents of which are incorporatedherein by reference.

DESCRIPTION

1. Technical Field

The present invention relates to mobile telecommunication networks,particularly but not exclusively networks operating according to the3GPP standards or equivalents or derivatives thereof. The invention hasparticular although not exclusive relevance to the Long Term Evolution(LTE) of UTRAN (called Evolved Universal Radio Access Network(E-UTRAN)).

2. Background Art

In a mobile telephone network, load balancing is required to sharescarcely available radio resources and the processing load betweenavailable base stations (referred to as eNBs in E-UTRAN). In order thatthis load balancing can take place, load measurements are made by thebase stations and shared with the neighbouring base stations, so thatdecisions on load balancing can be taken. In the RAN1#51B is meeting inSeville 14 to 18 Jan. 2008, the load balancing mechanism was discussed.In particular, RAN1 discussed the physical layer measurements needed tosupport efficient load balancing and agreed that the measurements of thephysical resource block usage in the uplink and the downlink arerelevant for load balancing. They have proposed the following fourdifferent measurements for this purpose:

-   -   1) Physical resource block usage for GBR (real time traffic) on        UL    -   2) Physical resource block usage for non-real traffic on UL    -   3) Physical resource block usage for GBR (real time) traffic on        DL    -   4) Physical resource block usage for non-real time traffic on DL

All these measurements are defined as a ratio (percentage) of the usedPhysical Resource Blocks (PRBs) for a type of traffic over the availablePRBs in the same direction over a certain time interval, and aremeasured per cell. Any non-scheduled transmissions and retransmissionsshould also be counted as used.

Further, RAN 1 believes that it would be sufficient if this control isdone at a periodicity in the order of seconds to minutes, or even at aslower rate depending on the expected traffic fluctuation such as forbusy hours.

However, details of the signalling of this information between the basestations for load balancing have yet to be defined.

Although for efficiency of understanding for those of skill in the artthe invention will be described in detail in the context of a 3G system,the principles of the handover procedure can be applied to othersystems, e.g. other COMA or wireless systems in which mobile devices orUser Equipment (UE) communicate with one of several other devices(corresponding to eNB) with the corresponding elements of the systemchanged as required.

DISCLOSURE OF INVENTION

Embodiments of the present invention aim to provide efficient techniquesfor signaling these measurements between the base stations.

According to one exemplary aspect, the present invention provides amethod performed by a EUTRAN base station comprising: sending a requestfor load balancing measurements to a neighbouring EUTRAN base station;receiving one or more resource status update messages from theneighbouring EUTRAN base station in response to the requested resourcestatus information; and performing load balancing operations independence upon the received one or more resource status messages.

The base station may also use load balancing measurements for itself anduse these also for performing the load balancing operations. Thesemeasurements may be measured directly by the base station.

The one or more status update messages may include data identifying thephysical resource block usage for real time and/or non-real time trafficon the uplink or the downlink.

The requesting base station may request the other base station toprovide the status updates at a specific time, periodically or inresponse to one or more specific events. The event may be, for example,when usage of a resource by the neighbouring base station exceeds adefined threshold and/or when the uplink interference level exceeds adefined threshold.

The request preferably defines a time period over which the loadmeasurements are obtained. Additionally, where the neighbouring basestation has a plurality of associated cells, the request may identify asubset of those cells for which the measurements are requested.

The base station can control handover of one or more associated mobilecommunication devices to another cell or base station in dependence uponthe one or more received resource status update messages. It can dothis, for example, by dynamically controlling Handover and Cellre-selection parameters in dependence upon the one or more receivedresource status update messages.

This exemplary aspect of the invention also provides a method performedby a EUTRAN base station comprising: receiving a request for resourcestatus information from a neighbouring EUTRAN base station; generatingone or more resource status update messages including one or more loadbalancing measurements; and sending the generated one or more resourcestatus update messages to the requesting base station.

The invention also provides corresponding base stations for performingthe above methods.

The invention provides, for all methods disclosed, correspondingcomputer programs or computer program products for execution oncorresponding equipment, the equipment itself (user equipment, nodes orcomponents thereof) and methods of updating the equipment.

An exemplary embodiment of the invention will now be described, by wayof example, with reference to the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a mobile telecommunication system of atype to which the exemplary embodiment is applicable;

FIG. 2 schematically illustrates a base station forming part of thesystem shown in FIG. 1;

FIG. 3 a schematically illustrates a signalling method for signallingthe load balancing measurements between two base stations;

FIG. 3 b schematically illustrates another signalling method forsignalling the load balancing measurements between two base stations;and

FIG. 3 c schematically illustrates a situation where a signallingfailure occurs between two base stations;

FIG. 3 d schematically illustrates one way in which termination may besignalled between two base stations;

FIG. 4 illustrates the way in which load information within a basestation can be used to dynamically control Handover and cell selectionparameters;

FIG. 5 schematically illustrates a simple resource status updateprocedure;

FIG. 6 schematically illustrates a master slave based resource statusupdate procedure;

FIG. 7 a schematically illustrates a common measurement like resourcestatus update procedure (successful initiation);

FIG. 7 b schematically illustrates a common measurement like resourcestatus update procedure (unsuccessful initiation);

FIG. 7 c schematically illustrates a common measurement like resourcestatus update procedure (termination);

FIG. 8 schematically illustrates a load information procedure; and

FIG. 9 illustrates a mechanism in which load information within an eNBcan be utilized to dynamically control Handover and Cell (Re-) Selectionparameters.

BEST MODE FOR CARRYING OUT THE INVENTION Overview

FIG. 1 schematically illustrates a mobile (cellular) telecommunicationsystem 1 in which users of mobile telephones (MT) 3-0, 3-1, and 3-2 cancommunicate with other users (not shown) via one of the base stations5-1 or 5-2 and a telephone network 7. A number of uplink and downlinkcommunications resources (sub-carriers, time slots etc) are availablefor the wireless link between the mobile telephones 3 and the basestations 5. In this exemplary embodiment, the base stations 5 allocatedownlink resources to each mobile telephone 3 depending on the amount ofdata to be sent to the mobile telephone 3. Similarly, the base stations5 allocate uplink resources to each mobile telephone 3 depending on theamount and type of data the mobile telephone 3 has to send to the basestation 5.

Each of the Base stations 5 includes an “S1” interface for interfacingwith the core telephone network 7 and an “X2” interface for interfacingwith neighbouring base stations 5. Load balancing measurements made bythe base stations 5 are sent to the neighbouring base stations 5 overthe X2 interface. In this exemplary embodiment, the measurement reportsare transmitted between the base stations 5 using a Master/Slavesignalling mechanism, in which a Master base station 5-1 requestsmeasurement reports from a Slave base station 5-2 in a defined formatand periodicity etc, and in which the Slave base station 5-2 responds inthe requested manner. Each base station 5 will act as Master whengathering load balancing information from neighbouring base stations 5and as a Slave when providing its own load balancing information toneighbouring base stations 5. In this way, each base station 5 canobtain the load balancing information it wants, at the periodicity itwants and in the format it wants. This makes interoperability betweendifferent makes of base station 5 easier and will significantly reduceunnecessary traffic over the X2 interface.

Base Station

FIG. 2 is a block diagram illustrating the main components of each ofthe base stations 5 used in this exemplary embodiment. As shown, eachbase station 5 includes a transceiver circuit 21 which is operable totransmit signals to and to receive signals from i) the mobile telephones3 via one or more antennae 23; ii) the telephone network 7 via the S1interface 24; and iii) other base stations 5 via the X2 interface 25. Acontroller 27 controls the operation of the transceiver circuit 21 inaccordance with software stored in memory 29. The software includes,among other things, an operating system 31, a load balancing module 32,a handover module 33 and a resource measurement module 34. The loadbalancing module 32 has a resource status request module 35 for issuingstatus requests to other base stations 5 requesting information on theload in the other base station 5; and a resource status update module 36for providing load information to other base stations 5 when requestedto do so. The Handover module 33 is responsible for controlling handoverof mobile telephones 3 to or from the base station 5. The Resourcemeasurement module 34 is responsible for obtaining the load informationdiscussed above (which is sent to other base stations 5 by the resourcestatus update module 36), ie:

-   -   1) Physical resource block usage for GBR (real time traffic) on        UL;    -   2) Physical resource block usage for non-real traffic on UL;    -   3) Physical resource block usage for GBR (real time) traffic on        DL; and    -   4) Physical resource block usage for non-real time traffic on        DL.

In the above description, the base station 5 is described for ease ofunderstanding as having a number of discrete modules (such as the loadbalancing module, handover module, resource measurement module etc).Whilst these modules may be provided in this way for certainapplications, for example where an existing system has been modified toimplement the invention, in other applications, for example in systemsdesigned with the inventive features in mind from the outset, thesemodules may be built into the overall operating system or code and sothese modules may not be discernible as discrete entities.

Load Balancing—Signalling Mechanism

In this exemplary embodiment, the base stations 5 selectively provideload information when requested by their neighbours. A base station 5-1may request a neighbouring base station 5-2 to send load information inthe format it likes (based on the Radio Resource Management (ARM)algorithm that is implemented by the requesting base station 5-1). Forexample the requesting base station 5-1 may indicate in a ResourceStatus Request (generated by the resource status request module 35) tothe neighbouring base stations 5-2 if it needs load information to bereported just once, or periodically, or in an event driven fashionwhenever any of one or more events occurs. The base station 5-2 thatreceives the request then responds at the appropriate time/event in aResource Status Update (generated by the Resource status update module36). In this way, the requesting base station 5-1 is acting as a“Master” and the responding base station 5-2 is acting as a “Slave”. Thescheduling used is illustrated in FIG. 3 a.

Details of Resource Status Request Message

The Master base station 5-1 will send a Resource Status Request to theSlave base station 5-2 requesting it to report its physical resourceblock usage information. The Resource Status Request will include aReporting Characteristics Information Element (IE), which indicateswhether this reporting shall be once, or periodically, or event driven,in which case the event is also specified. If the ReportingCharacteristics IE is not set, then, in this embodiment, the Slave basestation 5-2 shall send the Resource Status Update only once.

In this exemplary embodiment, a separate message to stop the ResourceStatus Update is not needed. Instead, the Master base station 5-1 sendsthe same request message, with the Reporting Characteristics IE valueset to zero. The Slave base station 5-2 shall interpret this message asa request to stop the Resource Status Update reporting, which it willprocess immediately and acknowledge with a similar value of zero in acorresponding Resource Status Update message.

Where the Resource Status Request message requests event triggeredreports for multiple events, it may also specify thresholds for thoseevents. For example, the Master base station 5-1 may request a Slavebase station 5-2 to report to it whenever its Total Physical ResourceBlock usage is above 95%, indicating a near congestion situation.Similarly, the Slave may be asked to report if the downlink transmittedpower exceeds a certain threshold value.

In this exemplary embodiment, the Resource Status Request messagegenerated by the Master base station 5-1 may include the “AveragingTime” to specify the measurement interval for producing the informationrequested by the Master base station 5-1. If this value is notspecified, then the Slave base station will apply a default value.

In this exemplary embodiment, the Resource Status Request messagegenerated by the Master base station 5-1 may include a Reporting Time tospecify a periodic reporting based on the Master bases station'sinternal ARM algorithm. If this value is not specified, the Slave basestation 5-2 may apply a default value.

As will be understood by those skilled in the art, each base station 5may control several different cells and, in this embodiment. TheResource Status Request message generated by the Master base station 5-1may also include the cell Id's of the cells for which it is interestedin receiving the resource load information. If this value is notspecified, the slave base station 5-2 will report the resource loadstatus of all its cells.

Details of Resource Status Update Message

In this exemplary embodiment, the Resource Status Update message shallinclude a Reporting Characteristics IE to indicate the reason for thereport. A couple of values in the Reporting Characteristics IE could bereserved to indicate congestion in the cell either in the UL or in theDL direction in terms of Physical layer resources or any other type ofprocessing resources. A Resource Status Update message with a congestionindication can also be autonomously sent by Slave base stations 5-2 tothe neighbouring Master base stations 5-1 who have requested Resourcestatus updates whenever congestion is detected. Further, the Slave basestations 5-2 can autonomously send the Resource Status Update messagewhen the congestion is resolved. A Resource Status Update message canalso be autonomously sent by a Slave base station 5-2 to theneighbouring Master base stations 5-1 who have requested Resource statusupdates whenever UL interference exceeds a particular threshold in itsown cell, thus incorporating the existing procedure “Load Information”in it.

The Resource Status Update message will also include the relevantmeasurements requested by the Master base station 5-1:

-   -   1) Averaged Physical resource block usage for real time traffic        on UL based on the Averaging/ Reporting Time specified by the        Master base station 1;    -   2) Averaged Physical resource block usage for non-real traffic        on UL based on the Averaging/ Reporting Time specified by the        Master base station 5-1;    -   3) Averaged Physical resource block usage for real time traffic        on DL based on the Averaging/ Reporting Time specified by the        Master base station 5-1; and    -   4) Averaged Physical resource block usage for non-real time        traffic on DL based on the Averaging/ Reporting Time specified        by the Master base station 5-1.

As mentioned above, in general, each base station 5 will have both theMaster (in Asking Resource Status Information) and Slave (ProvidingResource Status Reports) roles. However, a base station 5 may notimplement a load balancing algorithm and in this case shall act only asa Slave in providing the Resource Status Reports to neighbouring basestations 5, which may be considered to be mandatory.

In an alternative exemplary embodiment, there could be a moresophisticated procedure where the Slave base station 5-2 responds to aResource Status Request such as in the manner illustrated in FIG. 3 b,where there is a successful initiation and in FIG. 3 c, where theinitiation failed. The initial failure may be because the Slave basestation 5-2 does not support the requested measurements. However, if itis mandatory for each Base station 5 to provide Resource Status updatemessages to other neighbouring base stations 5, then such aresponse/failure message may not be needed. In addition, a positive stopor termination message may also be sent to terminate the signallingbetween the Master and Slave base stations 5 (see, FIG. 3 d).

As those skilled in the art will appreciate, with the signallingdiscussed above, load reporting can be performed based on the Reportingperiod specified by the Master base station 51, thereby allowing theMaster base station 5-1 to effectively utilize the received resourcestatus information even in a multi vendor scenario, where implementationspecific algorithms are run in different base stations 5. Furthermore,redundant signalling over the X2 interface 25 can be reduced.

Load Information Procedure

Presently 3GPP Standard document TS 36.423 defines a Load InformationProcedure, the purpose of which is to transfer the uplink InterferenceOverload Indication between intra-frequency neighboring base stations 5for interference coordination purposes. Overload Indications are sentwhen the base station 5 experiences too high interference levels in theUL on some resource blocks due to a mobile telephone 3 at the cell edgeusing high power to transmit UL data. Base stations 5 that receive thismessage, should in principle, ask the mobile telephone 3 to reduce theUL transmit power that is causing the interference.

A base station 5 initiates the procedure by sending a Load Informationmessage to intra-frequency neighbouring base stations 5. The Loadinformation Procedure is used to send interference overload indicationswhen the base station 5 experiences too high interference levels on someresource blocks.

The Resource Status update procedure described above can incorporatethis Load Information Procedure if the Resource Status Update messagescan be autonomously sent by the Slave base stations 5-2 to theneighbouring Master base stations 5-1 that have requested the Resourcestatus update and have intra frequency cells whenever the ULinterference exceeds a particular threshold in its own cell. Such amerged procedure could be called either a Resource Status Update or LoadInformation Procedure, whichever is more appropriate.

Associated SON Functionality

The load information obtained by the base station 5 in the above mannercan be utilized to dynamically control Handover and Cell (Re-)Selectionparameters of a cell controlled by the base station 5, through aninternal SON entity (which is a self organizing Network that providesARM functionality within the base station 5). In other words, the loadinformation obtained can be used to control how the base station 5selects which cell a mobile telephone 5 should be passed to as thetelephone 3 roams within the network's coverage area. This isillustrated in FIG. 4.

Cell re-selection parameters that could be updated include:

-   -   1. Inter-frequency reselection priorities    -   2. layer specific offset

(How to apply it to the Intra frequency case is FFS (for further study)as it is based on ranking of cells.)

Hand Over parameters that can be configured include:

-   -   1. Hysteresis    -   2. Time to trigger    -   3. etc.

MODIFICATIONS AND ALTERNATIVES

A detailed exemplary embodiment has been described above. As thoseskilled in the art will appreciate, a number of modifications andalternatives can be made to the above embodiment whilst still benefitingfrom the inventions embodied therein.

In the above exemplary embodiment, a mobile telephone basedtelecommunications system was described. As those skilled in the artwill appreciate, the signalling and handover techniques described in thepresent application can be employed in other communications system.Other communications nodes or devices may include user devices such as,for example, personal digital assistants, laptop computers, webbrowsers, etc.

In the above exemplary embodiments, a number of software modules weredescribed. As those skilled will appreciate, the software modules may beprovided in compiled or un-compiled form and may be supplied to the basestation or to the mobile telephone as a signal over a computer network,or on a recording medium. Further, the functionality performed by partor all of this software may be performed using one or more dedicatedhardware circuits. However, the use of software modules is preferred asit facilitates the updating of base station 5 and the mobile telephones3 in order to update their functionalities.

Various other modifications will be apparent to those skilled in the artand will not be described in further detail here.

GLOSSARY OF 3GPP TERMS

-   LTE—Long Term Evolution (of UTRAN)-   eNodeB—E-UTRAN Node B-   UE—User Equipment—mobile communication device-   DL—downlink—link from base to mobile-   UL—uplink—link from mobile to base-   MME—Mobility Management Entity-   UPE—User Plane Entity-   HO—Handover-   ALC—Radio Link Control-   ARC—Radio Resource Control-   ARM—Radio Resource Management-   SAE—System Architecture Evolution-   C-RNTI—Cell-Radio Network Temporary Identifier-   SIB—System Information Block-   U-plane—User Plane-   X2 Interface—Interface between two eNodeB-   S1 Interface Interface between eNodeB and MME-   TA—Tracking Area-   EPC—Evolved Packet Core-   AS—Access Stratum-   RNL—Radio Network Layer-   TNL—Transport Network Layer-   RACH—Random Access Channel-   MU MIMO—Multi-User Multi Input Multi Output-   DMRS—Demodulation Reference Signal Format-   MCS—Modulation and Coding Scheme

The following is a detailed description of the way in which the presentinventions may be implemented in the currently proposed 3GPP LTEstandard. Whilst various features are described as being essential ornecessary, this may only be the case for the proposed 3GPP LTE standard,for example due to other requirements imposed by the standard. Thesestatements should not, therefore, be construed as limiting the presentinvention in any way.

INTRODUCTION

In the RAN1#51Bis meeting, the load balancing mechanism was discussed. Areply LS in [1] has been sent to RAN 2 and RAN 3 to inform the outcomesof the agreements in RAN 1. In this contribution we provide furtherdetails about the signalling involved in order to have the achieve theload balancing.

Measurement Definitions

RAN1 has discussed the physical layer measurements needed to supportefficient load balancing and have agreed that the measurements of thephysical resource block usage in uplink and downlink are relevant forthis use case. They have proposed 4 different measurements listed belowfor this purpose

M1 Physical resource block usage for GBR (real time traffic) on UI

M2 Physical resource block usage for non-real traffic on UK

M3 Physical resource block usage for GBR (real time) traffic on DI

M4 Physical resource block usage for non-real time traffic on DI

All these measurements are defined as a ratio (percentage) of the usedPRBs for a type of traffic over the available PRBs in the some directionover a certain time interval, and are measured per cell. Anynon-scheduled transmissions and retransmissions should also be countedas used.

Further, RAN 1 believes that it is would be sufficient if this controlis done at a periodicity in the order of seconds to minutes, or even ata slower rate depending on the expected traffic fluctuation such as forbusy hours.

Details of the signalling for load balancing mechanism is yet to bedefined. In the next section we explore different options of how themeasured quantities are signalled over X2 interface and what parametersHandover and reselection parameters could be re-configured.

Signalling Over X2 4.1. All eNB Informs Measured Load Information toOther Neighbors

This is the simplest scenario where each eNBs informs measured loadinformation to all the neighbors to which they have an established X2connection by sending for example: Resource Status Update Messageperiodically. Alternatively, this information may be piggy-backed ondedicated messages.

As different vendors eNBs may implement different algorithms which wouldprocess the Resource Status Update Report at different intervals, usinga one fixed interval for reporting may result in reports being sent toofrequently and the eNB just discarding large number of these reports.For example if the Load balancing algorithm operates every 5 seconds, aResource Status Update reporting interval is fixed at say 1 sec then 4out of 5 reports may be discarded.

4.2. eNB Requests Load Information Selectively From Neighbor eNBs

An eNB may request the neighbouring eNB to send load information in thefashion it likes (based on the implemented ARM algorithm.) For examplethe requesting eNB may indicate in the Resource Status Request to theneighbouring eNB if it needs Load information to be reported just once,or periodically, or in an event driven fashion whenever any of thecorresponding multiple event occurs.

We call this as a Master Slave configuration where the requesting eNB isthe master and can request the information in the format it desires.

Details of Resource Status Request Message

-   -   Master eNB1 sends an Resource Status Request to Slave eNB2        requesting it to indicate the physical resource block usage        either once, or periodically, or event driven manner.    -   Reporting Characteristics IE indicates whether reporting shall        be once, or periodically, or event driven, in which case the        event is specified. If the reporting characteristics IE is not        set, then the Resource Status Update SHALL be sent only once by        the slave eNB (see FIG. 5).    -   Note that a separate message to Stop the Resource Status Update        need not be specified. The same request message, with Reporting        Characteristics value set to 0, shall be interpreted as a        request to stop the Resource Status Update reporting, which        shall be processed by the receiver immediately and acknowledged        with a similar value of 0 in the corresponding Resource Status        Update message    -   In the Resource Status Request message, the reporting        characteristics IE would allow the Master eNB to request either        periodic or event triggered reports for multiple events and the        possibility of providing the thresholds for these events.    -   In the Resource Status Request message, the Averaging Time could        be included by the Master eNB to specify a measurement interval        for producing the information requested by Master eNB. If this        value is not specified, the slave eNB shall apply a default        value    -   In the Resource Status Request message, the Reporting Time could        be included by the Master eNB to specify a reporting based on        its internal ARM algorithm. If this value is not specified, the        slave eNB shall apply a default value    -   In the Resource Status Request message, Master eNB could include        the cell Id's of the cells for which it is interested in        receiving the resource information. If this value is not        specified, the slave eNB shall report the resource status of all        the cells.

Details of Resource Status Update Message

-   -   Resource Status Update message shall also including Reporting        Characteristics IE to indicate the reason for this report.    -   In Reporting Characteristics IE,-couple of the values could        reserved to indicate congestion in the cell either in UL or in        DL direction in terms of Physical layer resources or any other        type of processing resources. Resource Status Update Report with        congestion indication can be autonomously sent by slave eNB to        the neighbouring Master eNBs who have requested Resource status        update whenever a congestion is detected. Further, slave eNB can        autonomously send the Resource Status Update Report when the        congestion is resolved. Resource Status Update Report could be        autonomously sent by slave eNB the neighbouring Master eNBs who        have requested Resource status update whenever UL interference        exceeds a particular threshold in its own cell. Thus        incorporating the existing procedure Load Information in it.    -   Averaged Physical resource block usage for GSR (real time        traffic) on UL based on the Averaging/ Reporting Time specified        by Master eNB    -   Averaged Physical resource block usage for non-real traffic on        UL based on the Averaging/ Reporting Time specified by Master        eNB    -   Averaged Physical resource block usage for GSR (real time)        traffic on DL based on the Averaging/ Reporting Time specified        by Master eNB    -   Averaged Physical resource block usage for non-real time traffic        on DL based on the Averaging/ Reporting Time specified by Master        eNB

It should be noted that in general each eNB is having both the Master(in Asking Resource Status Information) and Slave (Providing ResourceStatus Reports) roles. However, an eNB may not implement a loadbalancing algorithm and in this case shall act only as a slave inproviding the Resource Status report to neighbouring eNB which may beconsidered to be mandatory.

Alternatively we could have more sophisticated procedure similar toCommon Measurement Procedure defined in UMTS over lur interface wherethere is a response to a Resource Status Request such as Resource StatusResponse as shown in FIGS. 7 a, 7 b, and 7 c Compared to option 2 itprovides the eNB to reject the Resource Status Request in case it doesnot supported a requested measurements.

Such a procedure will require 5 messages as compared to Master SlaveConfiguration proposed in FIG. 6. However, if it is mandatory for eacheNB to provide Resource Status update to other neighbouring eNB thensuch a response/failure message may not be needed.

Such an options would allow reporting of the load information based onthe Reporting period specified by the Master eNB so that it couldeffectively utilize resource status information in multi vendor scenarioallowing the implementation specific algorithms perform efficiently.Furthermore, the redundant signalling over X2 could be reduced.

Relation to Load information Procedure

Presently Load information Procedure is defined in [3]. The purpose ofthe Load indication procedure is to transfer the uplink InterferenceOverload Indication between intra-frequency neighboring eNodeBs forinterference coordination purpose.

An eNodeB initiates the procedure by sending LOAD INFORMATION message tointra-frequency neighbouring eNodeBs (see, FIG. 8). The LOAD INFORMATIONmessage can carry interference overload indication. The Load indicationprocedure shall be used to send interference overload indication whenthe eNB experiences too high interference level on some resource blocks.

The proposed Resource Status update procedure can incorporate the aboveprocedure if the Resource Status Update Report could be autonomouslysent by slave eNB to the neighbouring Master eNBs who have requestedResource status update and have intra frequency cells whenever ULinterference exceeds a particular threshold in its own cell. Hence forthe sake of simplicity we propose to merge these to procedures together.We could call the merged procedure either as Resource Status Update orLoad Information Procedure, whichever seems more appropriate.

Associated SON Functionality

The Load Information within the eNB can be utilized to dynamicallycontrol Handover and Cell (Re-) Selection parameters of the cellcontrolled by eNB through internal SON entity. The mechanism is shown inFIG. 9.

Cell re-selection parameters that could be updated are. [How to apply itto Intra frequency case is FFS as it is based in ranking of cells.]

-   -   3. Inter-frequency reselection priorities    -   4. layer specific offset

Hand Over parameters that can be configured are

-   -   1. Hysteresis    -    Time to trigger    -   3. etc.

CONCLUSIONS

In this contribution we discuss various options for exchanginginformation about the Resource Status between eNBs. We believe thatMaster/Slave kind configuration would be very flexible in providing theresource status reports to the implementation specific ARM algorithms ina multi-vendor scenario and should be adopted. We urge RAN 3 to agree onthe proposed Master/Slave kind of reporting option and the associatedtext proposal in [4] for X2AP specs.

Further we also discuss the handover and Cell Reselection parametersthat could be optimized in the associated SON functionality and ifagreeable some details could be captured in Stage 2 TS.

REFERENCES

-   [1] R1-080601, Reply LS on Load balancing, RAN 1-   [2] 25.423 3GPP Specification for RNSAP-   [3] 36.423 3GPP Specifications for X2AP-   [4] R3-08XXXX Text procedure for Resource Status Update Procedure.

This application is based upon and claims the benefit of priority fromUnited Kingdom patent application No. 0802023.2, filed on Feb. 4, 2008,the disclosure of which is incorporated herein in its entirety byreference.

1. A method performed by a base station, the method comprising:generating a request for resource status information; sending thegenerated request to a neighboring base station; receiving one or moreresource status update messages from the neighboring base station inresponse to the requested resource status information; and performingload balancing operations in dependence upon the received one or moreresource status update messages.
 2. A method as claimed in claim 1,wherein the base station performing the method includes an E-UTRAN basestation.
 3. A method as claimed in claim 1, wherein the neighboring basestation includes an E-UTRAN base station.
 4. A method as claimed inclaim 1, wherein said one or more status update messages include dataidentifying a physical resource block usage for a guaranteed bit rate(GBR) traffic on a downlink.
 5. A method as claimed in claim 1, whereinsaid one or more status update messages include data identifying aphysical resource block usage for a non-guaranteed bit rate (GBR)traffic on a downlink.
 6. A method as claimed in claim 1, wherein saidone or more status update messages include data identifying a physicalresource block usage for a non-guaranteed bit rate (GBR) traffic on anuplink.
 7. A method performed by a base station, the method comprising:receiving a request for resource status information from a neighboringbase station; obtaining one or more load balancing measurements forresources associated with the base station; generating one or moreresource status update messages including the one or more load balancingmeasurements; and sending the generated one or more resource statusupdate messages to the neighboring base station.
 8. A base station,comprising: means for generating a request for resource statusinformation; means for sending the generated request to a neighboringbase station; means for receiving one or more resource status updatemessages from the neighboring base station in response to the requestedresource status information; and means for performing load balancingoperations in dependence upon the received one or more resource statusupdate messages.
 9. A base station, comprising: means for receiving arequest for resource status information from a neighboring base station;means for obtaining one or more load balancing measurements forresources associated with the base station; means for generating one ormore resource status update messages including the one or more loadbalancing measurements; and means for sending the generated one or moreresource status update messages to the neighboring base station.
 10. Abase station, comprising: a request generator operable to generate arequest for resource status information; a transceiver operable totransmit the generated request to a neighboring base station andoperable to receive one or more resource status update messages from theneighboring base station in response to the requested resource statusinformation; and a controller operable to perform load balancingoperations in dependence upon the received one or more resource statusupdate messages.
 11. A base station, comprising: a transceiver operableto receive a request for resource status information from a neighboringbase station; a controller operable to obtain one or more load balancingmeasurements for resources associated with the base station; and aresource status update message generator operable to generate one ormore resource status update messages including the one or more loadbalancing measurements, wherein said transceiver is operable to transmitthe generated one or more resource status update messages to theneighboring base station.
 12. A mobile terminal configured for handover,from a base station adapted to perform a method according to claim 1,and in accordance with said load balancing operations performed by saidbase station.
 13. A communication system, comprising: a requestgenerator operable to generate a request for resource statusinformation; a transceiver operable to transmit the generated request toa neighboring base station and operable to receive one or more resourcestatus update messages from the neighboring base station in response tothe requested resource status information; a controller operable toperform load balancing operations in dependence upon the received one ormore resource status update messages; and a mobile terminal configuredfor handover from said base station in accordance with said loadbalancing operations performed by said base station.
 14. Anon-transitory computer-readable storage medium tangibly embodying aprogram of machine-readable instructions executable by a digitalprocessing apparatus to perform the method of claim
 1. 15. Anon-transitory computer-readable storage medium tangibly embodying aprogram of machine-readable instructions executable by a digitalprocessing apparatus to perform the method of claim 7.